In the table above, is z = 20q ?

Question

https://gmatclub.com/forum/download/file.php?id=20446 In the table above, is z = 20q ? (1) q = 3 (2) Each value in the table other than q is equal to the sum of the value immediately above it in the table and the value immediately to its left in the table qqqq.png

Bunuel · Accepted Answer

https://gmatclub.com/forum/download/file.php?id=20446 In the table above, is z = 20q? (1) q = 3 --> we don't know the relationship between the letters. Not sufficient. (2) Each value in the table other than q is equal to the sum of the value immediately above it in the table and the value immediately to its left in the table --> we can express all letters below and to the right of q in terms of q and eventually we'll get z in terms of q and see whether z=20q is true. Sufficient. Answer: B. Just to illustrate: untitled.PNG

TehJay · Answer

1) q=3 tells us nothing about z. Insufficient.

2) From this, we have:

z=w+y 
 w+y = (t+v) + (v+x) = t+2v+x 
 t+2v+x = (q+s) + 2(s+u) + (u+q) = 2q + 3s + 3u 
 2q + 3s + 3u = 2q + 3(q+r) + 3(r+q) = 8q + 6r 
 8q + 6r = 8q + 6(q+q) = 20q

So z = 20q. Sufficient.

fozzzy · Answer

How common are such questions on the GMAT and what's the difficulty level if this question shows up as Problem solving rather than DS? Bunuel's approach is easier to digest

paisaj87 · Answer

I got the answer right, but it took me arounf 4 mins. 
Lots of equations to set up!

EMPOWERgmatRichC · Answer

Hi All,

GMAT questions can often be solved using variety of different approaches (and even the "math" can be done in different ways), so you sometimes have to think about what is the easiest way to get to the answer using the given information (and using the wording of the specific question to your advantage).

Here, we're asked if Z = 20Q, which is a relatively "strange" thing to ask. Maybe there's a pattern to figuring out that exact question....

Everyone seems to have interpreted Fact 1 correctly, so I won't rehash that work here.

In Fact 2, we're told that each value that is NOT a Q is equal to the SUM of the value directly to the LEFT and directly ABOVE it. Using the table, we start with....

Q Q Q Q
Q
Q
Q

From here, let's do the second row, but don't write down a thick equation for every box - just talk through the math....

Q + Q = 2Q

Q Q Q Q
Q 2Q
Q
Q

Q + 2Q = 3Q

Q Q Q Q
Q 2Q 3Q
Q
Q

Q + 3Q = 4Q

Q Q Q Q
Q 2Q 3Q 4Q
Q
Q

You can easily fill in the next two rows without that much effort - just add up the values to the immediate LEFT and ABOVE....

Q Q Q Q
Q 2Q 3Q 4Q
Q 3Q 6Q 10Q
Q 4Q 10Q 20Q

When a question takes you "too long" to answer, sometimes what you have to focus on is how YOU approached the task. Could you have organized your work better? Could you have done the math in a different way? Could you have used a different approach entirely? Etc. As such, it's often beneficial to redo past questions (even if you got the questions correct) so that you can master other approaches and ultimately be able to approach questions in multiple ways. That flexibility in thinking will be beneficial on Test Day.

GMAT assassins aren't born, they're made,
Rich

SinhaS · Answer

Hi Bunuel,

I think it's a silly question, but if z=12Q after the derivation, then also the answer would be B as the data is sufficient to say that z is not equal to 20Q, just a general query.

Bunuel · Answer

Yes. In a Yes/No Data Sufficiency questions, statement(s) is sufficient if the answer is “always yes” or “always no” while a statement(s) is insufficient if the answer is "sometimes yes" and "sometimes no".

When a DS question asks about the value of some variable, then the statement(s) is sufficient ONLY if you can get the single numerical value of this variable.

Hope it helps.

sahilvijay · Answer

1) q=3 => insufficient
2) Each value in the table other than q is equal to the sum of the value immediately above it in the table and the value immediately to its left in the table

q-q--q--q
q-2q-3q-4q
q-3q-6q-10q
q-4q-10q-20q

Clearly z=20q

Option B is the correct answer

KarishmaB · Answer

Such a question is not hard if you choose the right starting point.
Statement 1 is obviously not sufficient since it doesn't give the relation between variables. 
So look at Statement 2. You want to see if you can get z in terms of q.
Note that r on the edge can be written in terms of q only. 
r = 2q
So s = 3q, t = 4q.
Similarly, we will get u, v and w in terms of q and eventually x, y and z in terms of q.

So we will know whether z is equal to 20q and statement 2 alone will be sufficient.

Answer (B)

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In the table above, is z = 20q ?

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GMAT Data Sufficiency (DS) Questions

In the table above, is z = 20q ?

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